The present invention relates to orthopedic medical apparatus and more particularly to medical apparatus used to treat fractured bones which are repositioned and immobilized by fixation means external to the soft body tissue. Such medical apparatus are referred to very broadly as external fixation devices. The present invention relates directly to fastening means which hold surgical fixation pins in fixation frame structures, which fastening means are also used to apply tension to the fixation pins penetrating the fractured bones so as to more securely position and immobilize the fractured bones.
External fixation has long been recognized as a viable means of treating bone fractures. A recent new external fixation device is described in U.S. Pat. No. 4,450,834 issued May 29, 1984 to David A. Fischer which patent is here incorporated by reference as there fully set forth. The external fixation device disclosed in U.S. Pat. No. 4,450,834 comprises a pair of arcuate frame segements which cooperate together as well as with a plurality of surgical fixation pins secured and mounted to the arcuate frame segments. The invention therein disclosed also comprises pin holders which were positioned at various locations upon the arcuate frame segment. The holders secured the surgical fixation pins to the arcuate frame segments so as to securely position the fractured bone, through which, pass the surgical fixation pins.
There, the pin holders of the claimed invention have an elongated body which includes a plurality of horizontal apertures which extend through the width of the body. Each aperture is sized to loosely receive a convention surgical fixation pin. The elongated body also includes a plurality of rectangular vertical pockets formed perpendicularly to the horizontal apertures. The pockets extend from an upper surface of the pin holder and terminate at some distance below the horizontal apertures but above the lower surface of the elongated body. Each of the vertical pockets are sized to slidely receive a pin lock member having a rectangular shaped body and a threaded stud. The body of the pin lock member includes a central aperture also for losely receiving a fixation pin.
In operation, the pin lock is losely vertically inserted down into one of the pockets formed in the elongated body. A surgical fixation pin is horizontally inserted through the aperture formed in the elongated body as well as the horizontal aperture formed in the pin lock. Subsequently, an acorn fastener is threadedly mounted onto the stud causing the pin lock to be pulled tightly downward against the surgical fixation pin thereby accurately centering the pin within the pin holder and securely locking the fixation pin into position by the concentric forces exerted along the contact surface between the outer diameter of the surgical fixation pin and the aperture surfaces of both the elongated body and the pin lock.
The pin holders do not provide for a tension force upon the surgical fixation pin along its length for rigidly holding the fixation pin thereby enabling limited bowing of the fixation pin. Hence, the surgical fixation device disclosed in the prior art patent lacks suitable means for applying tension to the surgical fixation pin preventing bowing. This inability to apply tension along the length of the surgical fixation pins permits movement of the fractured bone positioned and secured by the external fixation device. Such movement of the fractured bone may delay the healing process or may cause the fractured bones to heal incorrectly requiring further surgery or resulting in permanent disfigurement of the bone.
The surgeon needs to operate quickly and efficiently so as to minimize incorrect healing processes prior to correct fixation of the fractured bone in the external fixation device. Thus, another disadvantage with the pin holder of the prior art patent is the complex structure of the pin holder which is difficulty manipulated during surgical operations addressing fractured bones.
During operations, the surgeon must place a plurality of pin locks through apertures in the elongated body of the pin holder. These pin locks are small and have the corresponding small apertures which require the utmost dexterity of the surgeon during the surgical operation. From time to time, such lock pins may be dropped or otherwise mishandled during the surgical process. These and other disadvantages are solved or minimized using a surgical fixation pin tension adjuster of an external fixation device.